2010/10/28 Uwe Ligges <lig...@statistik.tu-dortmund.de>: > > > On 28.10.2010 06:50, Lao Meng wrote: >> >> Hi all: >> I have a dataset which contains two variables: Y and time >> y<-c(228,189,232,198,252,315) >> time<-2003:2008 >> >> How can I find out the trend(increase/decrease) of y along the time >> period? >> >> If I use: >> lm(y~time) >> >> The "lm" command treats time as natural number,but not date. > > What is "date"? WHere is the reproducible example?
The code the poster displayed is reproducible -- the problem is more that its not entirely clear what is desired. If the worry is that there can be different numbers of days in different years due to leap years then one could use the number of days between January 1st of each year and January 1st of the first year like this (where y and time are from the original post): > d <- as.Date(paste(time, 1, 1, sep = "-")) > d <- as.numeric(d - d[1]) > d [1] 0 365 731 1096 1461 1826 > lm(y ~ d) Call: lm(formula = y ~ d) Coefficients: (Intercept) d 193.52454 0.04615 -- Statistics & Software Consulting GKX Group, GKX Associates Inc. tel: 1-877-GKX-GROUP email: ggrothendieck at gmail.com ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
